Novel Testing

Novel testing solution solves encryption testing problem

Testing of mobile handsets generally involves a device traditionally referred to as a system simulator. This simulates a GSM base station and network infrastructure and can thus be used to verify protocols used by mobiles to communicate with the network infrastructure.

Where encryption exists, for example the ciphering performed within GSM layer 1, the encryption algorithm must be disclosed to the test equipment manufacturer and incorporated into the system simulator. Correct ciphering and deciphering by the mobile device can be verified by testing it against the reference algorithms implemented inside the system simulator.

Analytek were approached with a more unusual request related to encryption. Mobiles are available on the market with additional encryption built into the mobile handset. Our customer wanted to verify the encryption of information sent between such mobiles.

This highlighted two problems with the traditional approach:

The encryption algorithms used between the mobile devices are proprietary and not available to test equipment manufacturers;

The encryption exists between the two mobile devices rather than between the device and a component in the network infrastructure.

Analytek devised a clever way to test this and other applications in the Mobile to Mobile application. Based on the Data Test Suite software already available from Analytek, it was possible to develop an application which linked two instruments running the Data Test Suite via the Data Test Suiteâ??s API.

With an encrypting mobile connected to each Data Test Suite, a mobile originating call on one mobile triggers a mobile terminating call on the other mobile. Once the call is established between the two mobiles, the encryption algorithms can negotiate an encrypted link exactly as they would on a live network. Since the mobiles are effectively tested back-to-back there is no requirement to implement the encryption algorithm in the test equipment.

Detailed logging of all traffic between the mobiles is performed so that the customer can verify that encryption is being successfully negotiated.

In addition to speech calls, the Mobile to Mobile application supports both circuit switched and GPRS data sessions, and short message transfers. This is particularly important since encrypting mobiles may exchange keys using SMS.

Since developing this application, Analytek have discovered several more niche areas of testing where the Mobile to Mobile application is extremely powerful: